1. Field of the Invention
This invention relates to apparatus and methods for migrating data, and more particularly to apparatus and methods for migrating thin-provisioned volumes in tiered storage architectures.
2. Background of the Invention
Customer growth over time varies and is often difficult to predict. As a result, it is often difficult to design and allocate storage resources that will adequately accommodate customer growth over a period of time while still ensuring that the storage resources are used in an efficient manner. Allocated but unused storage space increases up front costs, hardware, and power consumption. Thus, there is a powerful incentive to ensure that storage resources are allocated in an efficient manner. This involves a careful balancing act to ensure that enough storage space is available to accommodate growth while not allocating too much storage space that unnecessarily increases costs.
One current solution to the above-stated problem is to implement thin provisioning. Thin provisioning allows storage space to be allocated on a just-enough and just-in-time basis as data is written. This differs from conventional storage allocation techniques (also called “fat provisioning”) which allocates storage space up front and often results in large amounts of unused storage space. Thin provisioning, by comparison, eliminates most of the free space in storage volumes and helps to avoid poor storage utilization rates, often as low as ten percent, that occur using traditional “fat provisioning” allocation techniques. When properly implemented, thin provisioning can significantly reduce the amount of time system administrators spend allocating and managing storage.
In tiered storage architectures, different types of data are stored on different types of storage media in order to reduce total storage cost. The media on which data is stored may be based on desired levels of protection, performance requirements, frequency of use, and other considerations. As the characteristics of the data change, the data may be moved between tiers. For example, data that is accessed more frequency (i.e., is “hotter”) may be moved to faster storage media to improve performance. Unfortunately, some tiered storage architectures do not support migrating thin-provisioned volumes from one storage tier to another. This can be a disadvantage as both tiered storage architectures and thin-provisioning become more common.
In view of the foregoing, what are needed are apparatus and methods to migrate thin-provisioned volumes between tiers of a tiered storage architecture. Ideally, such apparatus and methods will also be effective to migrate standard volumes. Further needed are apparatus and methods to enable standard volumes to be converted to thin-provisioned volumes at the time of migration.